Java / Gaurang Jadia

I wrote this small basic Calculator Swing Program for my CS202 Assignment at Cal State LA. I thought to share with you all.

package lab8;

import java.awt.BorderLayout;
import java.awt.GridLayout;
import java.awt.event.ActionEvent;
import java.awt.event.ActionListener;
import java.awt.event.FocusEvent;

import javax.swing.JButton;
import javax.swing.JFrame;
import javax.swing.JPanel;
import javax.swing.JTextField;

public class Calculator extends JFrame implements ActionListener{

	private static final long serialVersionUID = 1L;
	
	int intState;
	String strOperand1;
	String strOperand2;
	String strOperation;
	boolean blnDot = false;
	JTextField jtxtfieldDisplayBar;
	JFrame jfCalculator = this;

	public Calculator(){
		super("Simple Calculator");
		this.setSize(300, 175);
		this.setLocationRelativeTo(null);
		this.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
		this.setResizable(false);

		FocusEvent focusEvent = new FocusEvent(this, FocusEvent.FOCUS_GAINED);
		dispatchEvent(focusEvent);

		intState = 0;
		strOperand1 = "";
		strOperand2 = "";
		strOperation = "";

		JPanel jpMain = new JPanel();
		jpMain.setLayout(new BorderLayout());
		this.add(jpMain);

		JPanel jpNorth = new JPanel();
		jpNorth.setLayout(new BorderLayout());
		jpMain.add(jpNorth, BorderLayout.NORTH);

		jtxtfieldDisplayBar = new JTextField("0");
		jtxtfieldDisplayBar.setHorizontalAlignment(JTextField.RIGHT);
		jtxtfieldDisplayBar.setEditable(false);
		jpNorth.add(jtxtfieldDisplayBar, BorderLayout.NORTH);

		JPanel jpNorthSouth = new JPanel();
		jpNorthSouth.setLayout(new GridLayout(1, 2));
		jpNorth.add(jpNorthSouth, BorderLayout.SOUTH);

		JButton jbtnBackspace = new JButton("Backspace");
		jbtnBackspace.addActionListener(this);
		jpNorthSouth.add(jbtnBackspace);

		JButton jbtnC = new JButton("C");
		jbtnC.addActionListener(this);
		jpNorthSouth.add(jbtnC);

		JPanel jpSouth = new JPanel();
		jpSouth.setLayout(new GridLayout(4, 5));
		jpMain.add(jpSouth, BorderLayout.CENTER);

		JButton jbtn7 = new JButton("7");
		jbtn7.addActionListener(this);
		jpSouth.add(jbtn7);
		JButton jbtn8 = new JButton("8");
		jbtn8.addActionListener(this);
		jpSouth.add(jbtn8);
		JButton jbtn9 = new JButton("9");
		jbtn9.addActionListener(this);
		jpSouth.add(jbtn9);
		JButton jbtnDivide = new JButton("/");
		jbtnDivide.addActionListener(this);
		jpSouth.add(jbtnDivide);
		JButton jbtnSquareRoot = new JButton("sqrt");
		jbtnSquareRoot.addActionListener(this);
		jpSouth.add(jbtnSquareRoot);

		JButton jbtn4 = new JButton("4");
		jbtn4.addActionListener(this);
		jpSouth.add(jbtn4);
		JButton jbtn5 = new JButton("5");
		jbtn5.addActionListener(this);
		jpSouth.add(jbtn5);
		JButton jbtn6 = new JButton("6");
		jbtn6.addActionListener(this);
		jpSouth.add(jbtn6);
		JButton jbtnMultiply = new JButton("*");
		jbtnMultiply.addActionListener(this);
		jpSouth.add(jbtnMultiply);
		JButton jbtnSquare = new JButton("x^2");
		jbtnSquare.addActionListener(this);
		jpSouth.add(jbtnSquare);

		JButton jbtn1 = new JButton("1");
		jbtn1.addActionListener(this);
		jpSouth.add(jbtn1);
		JButton jbtn2 = new JButton("2");
		jbtn2.addActionListener(this);
		jpSouth.add(jbtn2);
		JButton jbtn3 = new JButton("3");
		jbtn3.addActionListener(this);
		jpSouth.add(jbtn3);
		JButton jbtnSubstrate = new JButton("-");
		jbtnSubstrate.addActionListener(this);
		jpSouth.add(jbtnSubstrate);
		JButton jbtnUpon = new JButton("1/x");
		jbtnUpon.addActionListener(this);
		jpSouth.add(jbtnUpon);

		JButton jbtn0 = new JButton("0");
		jbtn0.addActionListener(this);
		jpSouth.add(jbtn0);
		JButton jbtnPM = new JButton("+/-");
		jbtnPM.addActionListener(this);
		jpSouth.add(jbtnPM);
		JButton jbtnDot = new JButton(".");
		jbtnDot.addActionListener(this);
		jpSouth.add(jbtnDot);
		JButton jbtnAdd = new JButton("+");
		jbtnAdd.addActionListener(this);
		jpSouth.add(jbtnAdd);
		JButton jbtnEqual = new JButton("=");
		jbtnEqual.addActionListener(this);
		jpSouth.add(jbtnEqual);
	}

	public static void main(String args[]){
		Calculator objSC = new Calculator();
		objSC.setVisible(true);
	}

	public void actionPerformed(ActionEvent e){
		String strCommand = e.getActionCommand();

		if(strCommand.equals("Backspace")){
			intState = 0;
			if(jtxtfieldDisplayBar.getText().length() == 0){
				jtxtfieldDisplayBar.setText("0");
			}
			else{
				String strTemp = jtxtfieldDisplayBar.getText(); 
				jtxtfieldDisplayBar.setText(strTemp.substring(0, (strTemp.length()-1)));
				strTemp = jtxtfieldDisplayBar.getText();
				if(strTemp.length() == 0){
					jtxtfieldDisplayBar.setText("0");
				}
			}
			return;
		}

		if(strCommand.equals("C")){
			intState = 0;
			strOperand1 = "";
			strOperand2 = "";
			strOperation = "";
			jtxtfieldDisplayBar.setText("0");
			return;
		}

		if(strCommand.equals(".")){
			blnDot = true;
		}

		if(strCommand.equals("+/-")){
			if(strOperand1 == ""){
				intState = 1;
			}
			else{
				if(jtxtfieldDisplayBar.getText().equals(strOperand1)){
					intState = 1;
					Double dblTemp = -1 * Double.parseDouble(strOperand1);
					strOperand1 = "" + dblTemp;
					jtxtfieldDisplayBar.setText(strOperand1);
					return;
				}
				else if(jtxtfieldDisplayBar.getText().equals(strOperand2)){
					intState = 3;
					Double dblTemp = -1 * Double.parseDouble(strOperand2);
					strOperand2 = "" + dblTemp;
					jtxtfieldDisplayBar.setText(strOperand2);
					return;
				}
			}
		}

		if(strCommand.equals("sqrt")){
			intState = 1;
			if(Double.parseDouble(strOperand1) < 0){
				System.err.println("Square Root of negative is imaginary number");
			}
			else{
				Double dblTemp = Math.sqrt(Double.parseDouble(strOperand1));
				strOperand1 = "" + dblTemp;
				jtxtfieldDisplayBar.setText(strOperand1);
				return;
			}
		}

		if(strCommand.equals("x^2")){
			intState = 1;
			Double dblTemp = Math.pow(Double.parseDouble(strOperand1), 2);
			strOperand1 = "" + dblTemp;
			jtxtfieldDisplayBar.setText(strOperand1);
			return;
		}

		if(strCommand.equals("1/x")){
			intState = 1;
			Double dblTemp = 1 / Double.parseDouble(strOperand1);
			strOperand1 = "" + dblTemp;
			jtxtfieldDisplayBar.setText(strOperand1);
			return;
		}

		switch(intState){

		case 0:{
			if(strCommand.equals("1")){
				strOperand1 = "1";
				intState = 1;
				jtxtfieldDisplayBar.setText(strOperand1);
			}
			if(strCommand.equals("2")){
				strOperand1 = "2";
				intState = 1;
				jtxtfieldDisplayBar.setText(strOperand1);
			}
			if(strCommand.equals("3")){
				strOperand1 = "3";
				intState = 1;
				jtxtfieldDisplayBar.setText(strOperand1);
			}
			if(strCommand.equals("4")){
				strOperand1 = "4";
				intState = 1;
				jtxtfieldDisplayBar.setText(strOperand1);
			}
			if(strCommand.equals("5")){
				strOperand1 = "5";
				intState = 1;
				jtxtfieldDisplayBar.setText(strOperand1);
			}
			if(strCommand.equals("6")){
				strOperand1 = "6";
				intState = 1;
				jtxtfieldDisplayBar.setText(strOperand1);
			}
			if(strCommand.equals("7")){
				strOperand1 = "7";
				intState = 1;
				jtxtfieldDisplayBar.setText(strOperand1);
			}
			if(strCommand.equals("8")){
				strOperand1 = "8";
				intState = 1;
				jtxtfieldDisplayBar.setText(strOperand1);
			}
			if(strCommand.equals("9")){
				strOperand1 = "9";
				intState = 1;
				jtxtfieldDisplayBar.setText(strOperand1);
			}
			if(blnDot){
				strOperand1 = "0";
				intState = 1;
				jtxtfieldDisplayBar.setText("0");
			}
			break;
		}

		case 1:{
			if(blnDot){
				strOperand1 += ".";		
				blnDot = false;
			}
			if(strCommand.equals("1")){
				strOperand1 += "1";
			}
			if(strCommand.equals("2")){
				strOperand1 += "2";
			}
			if(strCommand.equals("3")){
				strOperand1 += "3";
			}
			if(strCommand.equals("4")){
				strOperand1 += "4";
			}
			if(strCommand.equals("5")){
				strOperand1 += "5";
			}
			if(strCommand.equals("6")){
				strOperand1 += "6";
			}
			if(strCommand.equals("7")){
				strOperand1 += "7";
			}
			if(strCommand.equals("8")){
				strOperand1 += "8";
			}
			if(strCommand.equals("9")){
				strOperand1 += "9";
			}
			if(strCommand.equals("0")){
				strOperand1 += "0";
			}
			if(strCommand.equals("+")){
				strOperation = "+";
				intState = 2;
			}
			if(strCommand.equals("-")){
				strOperation = "-";
				intState = 2;
			}
			if(strCommand.equals("*")){
				strOperation = "*";
				intState = 2;
			}
			if(strCommand.equals("/")){
				strOperation = "/";
				intState = 2;
			}
			jtxtfieldDisplayBar.setText(strOperand1);
			break;
		}

		case 2:{
			if(strCommand.equals("1")){
				strOperand2 = "1";
				intState = 3;
				jtxtfieldDisplayBar.setText(strOperand2);
			}
			if(strCommand.equals("2")){
				strOperand2 = "2";
				intState = 3;
				jtxtfieldDisplayBar.setText(strOperand2);
			}
			if(strCommand.equals("3")){
				strOperand2 = "3";
				intState = 3;
				jtxtfieldDisplayBar.setText(strOperand2);
			}
			if(strCommand.equals("4")){
				strOperand2 = "4";
				intState = 3;
				jtxtfieldDisplayBar.setText(strOperand2);
			}
			if(strCommand.equals("5")){
				strOperand2 = "5";
				intState = 3;
				jtxtfieldDisplayBar.setText(strOperand2);
			}
			if(strCommand.equals("6")){
				strOperand2 = "6";
				intState = 3;
				jtxtfieldDisplayBar.setText(strOperand2);
			}
			if(strCommand.equals("7")){
				strOperand2 = "7";
				intState = 3;
				jtxtfieldDisplayBar.setText(strOperand2);
			}
			if(strCommand.equals("8")){
				strOperand2 = "8";
				intState = 3;
				jtxtfieldDisplayBar.setText(strOperand2);
			}
			if(strCommand.equals("9")){
				strOperand2 = "9";
				intState = 3;
				jtxtfieldDisplayBar.setText(strOperand2);
			}
			if(blnDot){
				strOperand2 = "0";
				intState = 3;
				jtxtfieldDisplayBar.setText("0");
			}
			break;
		}

		case 3:{
			if(blnDot){
				strOperand2 += ".";		
				blnDot = false;
			}
			if(strCommand.equals("1")){
				strOperand2 += "1";
				jtxtfieldDisplayBar.setText(strOperand2);
			}
			if(strCommand.equals("2")){
				strOperand2 += "2";
				jtxtfieldDisplayBar.setText(strOperand2);
			}
			if(strCommand.equals("3")){
				strOperand2 += "3";
				jtxtfieldDisplayBar.setText(strOperand2);
			}
			if(strCommand.equals("4")){
				strOperand2 += "4";
				jtxtfieldDisplayBar.setText(strOperand2);
			}
			if(strCommand.equals("5")){
				strOperand2 += "5";
				jtxtfieldDisplayBar.setText(strOperand2);
			}
			if(strCommand.equals("6")){
				strOperand2 += "6";
				jtxtfieldDisplayBar.setText(strOperand2);
			}
			if(strCommand.equals("7")){
				strOperand2 += "7";
				jtxtfieldDisplayBar.setText(strOperand2);
			}
			if(strCommand.equals("8")){
				strOperand2 += "8";
				jtxtfieldDisplayBar.setText(strOperand2);
			}
			if(strCommand.equals("9")){
				strOperand2 += "9";
				jtxtfieldDisplayBar.setText(strOperand2);
			}
			if(strCommand.equals("0")){
				if(Double.parseDouble(strOperand2) == 0){
				}
				else{
					strOperand2 += "0";
					jtxtfieldDisplayBar.setText(strOperand2);
				}
			}
			if(strCommand.equals("+") || strCommand.equals("-") || strCommand.equals("*") || strCommand.equals("/")){
				if(strOperation.equals("+")){
					if(strOperand2 == ""){
						strOperation = strCommand;
					}
					else{
						double d = Double.parseDouble(strOperand1) + Double.parseDouble(strOperand2);
						strOperand1 = "" + d;
						strOperand2 = "";
						strOperation = strCommand;
						intState = 3;
						jtxtfieldDisplayBar.setText(strOperand1);
					}
				}
				if(strOperation.equals("-")){
					if(strOperand2 == ""){
						strOperation = strCommand;
					}
					else{
						double d = Double.parseDouble(strOperand1) - Double.parseDouble(strOperand2);
						strOperand1 = "" + d;
						strOperand2 = "";
						strOperation = strCommand;
						intState = 3;
						jtxtfieldDisplayBar.setText(strOperand1);
					}
				}
				if(strOperation.equals("*")){
					if(strOperand2 == ""){
						strOperation = strCommand;
					}
					else{
						double d = Double.parseDouble(strOperand1) * Double.parseDouble(strOperand2);
						strOperand1 = "" + d;
						strOperand2 = "";
						strOperation = strCommand;
						intState = 3;
						jtxtfieldDisplayBar.setText(strOperand1);
					}
				}
				if(strOperation.equals("/")){
					if(strOperand2 == ""){
						strOperation = strCommand;
					}
					else{
						double d = Double.parseDouble(strOperand1) / Double.parseDouble(strOperand2);
						strOperand1 = "" + d;
						strOperand2 = "";
						strOperation = strCommand;
						intState = 3;
						jtxtfieldDisplayBar.setText(strOperand1);
					}
				}
			}

			if(strCommand.equals("=")){
				if(strOperation.equals("+")){
					double d = Double.parseDouble(strOperand1) + Double.parseDouble(strOperand2);
					strOperand1 = "" + d;
					strOperand2 = "";
					intState = 1;
					jtxtfieldDisplayBar.setText(strOperand1);
				}
				if(strOperation.equals("-")){
					double d = Double.parseDouble(strOperand1) - Double.parseDouble(strOperand2);
					strOperand1 = "" + d;
					strOperand2 = "";
					intState = 1;
					jtxtfieldDisplayBar.setText(strOperand1);
				}
				if(strOperation.equals("*")){
					double d = Double.parseDouble(strOperand1) * Double.parseDouble(strOperand2);
					strOperand1 = "" + d;
					strOperand2 = "";
					intState = 1;
					jtxtfieldDisplayBar.setText(strOperand1);
				}
				if(strOperation.equals("/")){
					if(Double.parseDouble(strOperand2) == 0){
						System.err.println("Can not divid by zero.");
					}
					else{
						double d = Double.parseDouble(strOperand1) / Double.parseDouble(strOperand2);
						strOperand1 = "" + d;
						strOperand2 = "";
						intState = 1;
						jtxtfieldDisplayBar.setText(strOperand1);
					}
				}
			}
			break;
		}
		default:
			System.err.println("Into invalid state!");
		}
	}
}

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package lab8;

import java.awt.BorderLayout;

import java.awt.GridLayout;

import java.awt.event.ActionEvent;

import java.awt.event.ActionListener;

import java.awt.event.FocusEvent;

import javax.swing.JButton;

import javax.swing.JFrame;

import javax.swing.JPanel;

import javax.swing.JTextField;

public class Calculator extends JFrame implements ActionListener{

private static final long serialVersionUID = 1L;

int intState;

String strOperand1;

String strOperand2;

String strOperation;

boolean blnDot = false;

JTextField jtxtfieldDisplayBar;

JFrame jfCalculator = this;

public Calculator(){

super("Simple Calculator");

this.setSize(300, 175);

this.setLocationRelativeTo(null);

this.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);

this.setResizable(false);

FocusEvent focusEvent = new FocusEvent(this, FocusEvent.FOCUS_GAINED);

dispatchEvent(focusEvent);

intState = 0;

strOperand1 = "";

strOperand2 = "";

strOperation = "";

JPanel jpMain = new JPanel();

jpMain.setLayout(new BorderLayout());

this.add(jpMain);

JPanel jpNorth = new JPanel();

jpNorth.setLayout(new BorderLayout());

jpMain.add(jpNorth, BorderLayout.NORTH);

jtxtfieldDisplayBar = new JTextField("0");

jtxtfieldDisplayBar.setHorizontalAlignment(JTextField.RIGHT);

jtxtfieldDisplayBar.setEditable(false);

jpNorth.add(jtxtfieldDisplayBar, BorderLayout.NORTH);

JPanel jpNorthSouth = new JPanel();

jpNorthSouth.setLayout(new GridLayout(1, 2));

jpNorth.add(jpNorthSouth, BorderLayout.SOUTH);

JButton jbtnBackspace = new JButton("Backspace");

jbtnBackspace.addActionListener(this);

jpNorthSouth.add(jbtnBackspace);

JButton jbtnC = new JButton("C");

jbtnC.addActionListener(this);

jpNorthSouth.add(jbtnC);

JPanel jpSouth = new JPanel();

jpSouth.setLayout(new GridLayout(4, 5));

jpMain.add(jpSouth, BorderLayout.CENTER);

JButton jbtn7 = new JButton("7");

jbtn7.addActionListener(this);

jpSouth.add(jbtn7);

JButton jbtn8 = new JButton("8");

jbtn8.addActionListener(this);

jpSouth.add(jbtn8);

JButton jbtn9 = new JButton("9");

jbtn9.addActionListener(this);

jpSouth.add(jbtn9);

JButton jbtnDivide = new JButton("/");

jbtnDivide.addActionListener(this);

jpSouth.add(jbtnDivide);

JButton jbtnSquareRoot = new JButton("sqrt");

jbtnSquareRoot.addActionListener(this);

jpSouth.add(jbtnSquareRoot);

JButton jbtn4 = new JButton("4");

jbtn4.addActionListener(this);

jpSouth.add(jbtn4);

JButton jbtn5 = new JButton("5");

jbtn5.addActionListener(this);

jpSouth.add(jbtn5);

JButton jbtn6 = new JButton("6");

jbtn6.addActionListener(this);

jpSouth.add(jbtn6);

JButton jbtnMultiply = new JButton("*");

jbtnMultiply.addActionListener(this);

jpSouth.add(jbtnMultiply);

JButton jbtnSquare = new JButton("x^2");

jbtnSquare.addActionListener(this);

jpSouth.add(jbtnSquare);

JButton jbtn1 = new JButton("1");

jbtn1.addActionListener(this);

jpSouth.add(jbtn1);

JButton jbtn2 = new JButton("2");

jbtn2.addActionListener(this);

jpSouth.add(jbtn2);

JButton jbtn3 = new JButton("3");

jbtn3.addActionListener(this);

jpSouth.add(jbtn3);

JButton jbtnSubstrate = new JButton("-");

jbtnSubstrate.addActionListener(this);

jpSouth.add(jbtnSubstrate);

JButton jbtnUpon = new JButton("1/x");

jbtnUpon.addActionListener(this);

jpSouth.add(jbtnUpon);

JButton jbtn0 = new JButton("0");

jbtn0.addActionListener(this);

jpSouth.add(jbtn0);

JButton jbtnPM = new JButton("+/-");

jbtnPM.addActionListener(this);

jpSouth.add(jbtnPM);

JButton jbtnDot = new JButton(".");

jbtnDot.addActionListener(this);

jpSouth.add(jbtnDot);

JButton jbtnAdd = new JButton("+");

jbtnAdd.addActionListener(this);

jpSouth.add(jbtnAdd);

JButton jbtnEqual = new JButton("=");

jbtnEqual.addActionListener(this);

jpSouth.add(jbtnEqual);

}

public static void main(String args[]){

Calculator objSC = new Calculator();

objSC.setVisible(true);

}

public void actionPerformed(ActionEvent e){

String strCommand = e.getActionCommand();

if(strCommand.equals("Backspace")){

intState = 0;

if(jtxtfieldDisplayBar.getText().length() == 0){

jtxtfieldDisplayBar.setText("0");

}

else{

String strTemp = jtxtfieldDisplayBar.getText();

jtxtfieldDisplayBar.setText(strTemp.substring(0, (strTemp.length()-1)));

strTemp = jtxtfieldDisplayBar.getText();

if(strTemp.length() == 0){

jtxtfieldDisplayBar.setText("0");

}

return;

}

if(strCommand.equals("C")){

intState = 0;

strOperand1 = "";

strOperand2 = "";

strOperation = "";

jtxtfieldDisplayBar.setText("0");

return;

}

if(strCommand.equals(".")){

blnDot = true;

}

if(strCommand.equals("+/-")){

if(strOperand1 == ""){

intState = 1;

}

else{

if(jtxtfieldDisplayBar.getText().equals(strOperand1)){

intState = 1;

Double dblTemp = -1 * Double.parseDouble(strOperand1);

strOperand1 = "" + dblTemp;

jtxtfieldDisplayBar.setText(strOperand1);

return;

}

else if(jtxtfieldDisplayBar.getText().equals(strOperand2)){

intState = 3;

Double dblTemp = -1 * Double.parseDouble(strOperand2);

strOperand2 = "" + dblTemp;

jtxtfieldDisplayBar.setText(strOperand2);

return;

}

if(strCommand.equals("sqrt")){

intState = 1;

if(Double.parseDouble(strOperand1) < 0){

System.err.println("Square Root of negative is imaginary number");

}

else{

Double dblTemp = Math.sqrt(Double.parseDouble(strOperand1));

strOperand1 = "" + dblTemp;

jtxtfieldDisplayBar.setText(strOperand1);

return;

}

if(strCommand.equals("x^2")){

intState = 1;

Double dblTemp = Math.pow(Double.parseDouble(strOperand1), 2);

strOperand1 = "" + dblTemp;

jtxtfieldDisplayBar.setText(strOperand1);

return;

}

if(strCommand.equals("1/x")){

intState = 1;

Double dblTemp = 1 / Double.parseDouble(strOperand1);

strOperand1 = "" + dblTemp;

jtxtfieldDisplayBar.setText(strOperand1);

return;

}

switch(intState){

case 0:{

if(strCommand.equals("1")){

strOperand1 = "1";

intState = 1;

jtxtfieldDisplayBar.setText(strOperand1);

}

if(strCommand.equals("2")){

strOperand1 = "2";

intState = 1;

jtxtfieldDisplayBar.setText(strOperand1);

}

if(strCommand.equals("3")){

strOperand1 = "3";

intState = 1;

jtxtfieldDisplayBar.setText(strOperand1);

}

if(strCommand.equals("4")){

strOperand1 = "4";

intState = 1;

jtxtfieldDisplayBar.setText(strOperand1);

}

if(strCommand.equals("5")){

strOperand1 = "5";

intState = 1;

jtxtfieldDisplayBar.setText(strOperand1);

}

if(strCommand.equals("6")){

strOperand1 = "6";

intState = 1;

jtxtfieldDisplayBar.setText(strOperand1);

}

if(strCommand.equals("7")){

strOperand1 = "7";

intState = 1;

jtxtfieldDisplayBar.setText(strOperand1);

}

if(strCommand.equals("8")){

strOperand1 = "8";

intState = 1;

jtxtfieldDisplayBar.setText(strOperand1);

}

if(strCommand.equals("9")){

strOperand1 = "9";

intState = 1;

jtxtfieldDisplayBar.setText(strOperand1);

}

if(blnDot){

strOperand1 = "0";

intState = 1;

jtxtfieldDisplayBar.setText("0");

}

break;

}

case 1:{

if(blnDot){

strOperand1 += ".";

blnDot = false;

}

if(strCommand.equals("1")){

strOperand1 += "1";

}

if(strCommand.equals("2")){

strOperand1 += "2";

}

if(strCommand.equals("3")){

strOperand1 += "3";

}

if(strCommand.equals("4")){

strOperand1 += "4";

}

if(strCommand.equals("5")){

strOperand1 += "5";

}

if(strCommand.equals("6")){

strOperand1 += "6";

}

if(strCommand.equals("7")){

strOperand1 += "7";

}

if(strCommand.equals("8")){

strOperand1 += "8";

}

if(strCommand.equals("9")){

strOperand1 += "9";

}

if(strCommand.equals("0")){

strOperand1 += "0";

}

if(strCommand.equals("+")){

strOperation = "+";

intState = 2;

}

if(strCommand.equals("-")){

strOperation = "-";

intState = 2;

}

if(strCommand.equals("*")){

strOperation = "*";

intState = 2;

}

if(strCommand.equals("/")){

strOperation = "/";

intState = 2;

}

jtxtfieldDisplayBar.setText(strOperand1);

break;

}

case 2:{

if(strCommand.equals("1")){

strOperand2 = "1";

intState = 3;

jtxtfieldDisplayBar.setText(strOperand2);

}

if(strCommand.equals("2")){

strOperand2 = "2";

intState = 3;

jtxtfieldDisplayBar.setText(strOperand2);

}

if(strCommand.equals("3")){

strOperand2 = "3";

intState = 3;

jtxtfieldDisplayBar.setText(strOperand2);

}

if(strCommand.equals("4")){

strOperand2 = "4";

intState = 3;

jtxtfieldDisplayBar.setText(strOperand2);

}

if(strCommand.equals("5")){

strOperand2 = "5";

intState = 3;

jtxtfieldDisplayBar.setText(strOperand2);

}

if(strCommand.equals("6")){

strOperand2 = "6";

intState = 3;

jtxtfieldDisplayBar.setText(strOperand2);

}

if(strCommand.equals("7")){

strOperand2 = "7";

intState = 3;

jtxtfieldDisplayBar.setText(strOperand2);

}

if(strCommand.equals("8")){

strOperand2 = "8";

intState = 3;

jtxtfieldDisplayBar.setText(strOperand2);

}

if(strCommand.equals("9")){

strOperand2 = "9";

intState = 3;

jtxtfieldDisplayBar.setText(strOperand2);

}

if(blnDot){

strOperand2 = "0";

intState = 3;

jtxtfieldDisplayBar.setText("0");

}

break;

}

case 3:{

if(blnDot){

strOperand2 += ".";

blnDot = false;

}

if(strCommand.equals("1")){

strOperand2 += "1";

jtxtfieldDisplayBar.setText(strOperand2);

}

if(strCommand.equals("2")){

strOperand2 += "2";

jtxtfieldDisplayBar.setText(strOperand2);

}

if(strCommand.equals("3")){

strOperand2 += "3";

jtxtfieldDisplayBar.setText(strOperand2);

}

if(strCommand.equals("4")){

strOperand2 += "4";

jtxtfieldDisplayBar.setText(strOperand2);

}

if(strCommand.equals("5")){

strOperand2 += "5";

jtxtfieldDisplayBar.setText(strOperand2);

}

if(strCommand.equals("6")){

strOperand2 += "6";

jtxtfieldDisplayBar.setText(strOperand2);

}

if(strCommand.equals("7")){

strOperand2 += "7";

jtxtfieldDisplayBar.setText(strOperand2);

}

if(strCommand.equals("8")){

strOperand2 += "8";

jtxtfieldDisplayBar.setText(strOperand2);

}

if(strCommand.equals("9")){

strOperand2 += "9";

jtxtfieldDisplayBar.setText(strOperand2);

}

if(strCommand.equals("0")){

if(Double.parseDouble(strOperand2) == 0){

}

else{

strOperand2 += "0";

jtxtfieldDisplayBar.setText(strOperand2);

}

if(strCommand.equals("+") || strCommand.equals("-") || strCommand.equals("*") || strCommand.equals("/")){

if(strOperation.equals("+")){

if(strOperand2 == ""){

strOperation = strCommand;

}

else{

double d = Double.parseDouble(strOperand1) + Double.parseDouble(strOperand2);

strOperand1 = "" + d;

strOperand2 = "";

strOperation = strCommand;

intState = 3;

jtxtfieldDisplayBar.setText(strOperand1);

}

if(strOperation.equals("-")){

if(strOperand2 == ""){

strOperation = strCommand;

}

else{

double d = Double.parseDouble(strOperand1) - Double.parseDouble(strOperand2);

strOperand1 = "" + d;

strOperand2 = "";

strOperation = strCommand;

intState = 3;

jtxtfieldDisplayBar.setText(strOperand1);

}

if(strOperation.equals("*")){

if(strOperand2 == ""){

strOperation = strCommand;

}

else{

double d = Double.parseDouble(strOperand1) * Double.parseDouble(strOperand2);

strOperand1 = "" + d;

strOperand2 = "";

strOperation = strCommand;

intState = 3;

jtxtfieldDisplayBar.setText(strOperand1);

}

if(strOperation.equals("/")){

if(strOperand2 == ""){

strOperation = strCommand;

}

else{

double d = Double.parseDouble(strOperand1) / Double.parseDouble(strOperand2);

strOperand1 = "" + d;

strOperand2 = "";

strOperation = strCommand;

intState = 3;

jtxtfieldDisplayBar.setText(strOperand1);

}

if(strCommand.equals("=")){

if(strOperation.equals("+")){

double d = Double.parseDouble(strOperand1) + Double.parseDouble(strOperand2);

strOperand1 = "" + d;

strOperand2 = "";

intState = 1;

jtxtfieldDisplayBar.setText(strOperand1);

}

if(strOperation.equals("-")){

double d = Double.parseDouble(strOperand1) - Double.parseDouble(strOperand2);

strOperand1 = "" + d;

strOperand2 = "";

intState = 1;

jtxtfieldDisplayBar.setText(strOperand1);

}

if(strOperation.equals("*")){

double d = Double.parseDouble(strOperand1) * Double.parseDouble(strOperand2);

strOperand1 = "" + d;

strOperand2 = "";

intState = 1;

jtxtfieldDisplayBar.setText(strOperand1);

}

if(strOperation.equals("/")){

if(Double.parseDouble(strOperand2) == 0){

System.err.println("Can not divid by zero.");

}

else{

double d = Double.parseDouble(strOperand1) / Double.parseDouble(strOperand2);

strOperand1 = "" + d;

strOperand2 = "";

intState = 1;

jtxtfieldDisplayBar.setText(strOperand1);

}

break;

}

default:

System.err.println("Into invalid state!");

}

Gaurang Jadia

Nothing is permanent except change

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